In the context of environmental issues and safety requirements, power generation by sunlight or wind power has attracted attention. For example, there is a growing number of households that introduce a photovoltaic power generation system. In the photovoltaic power generation system, the power generated by a photovoltaic module is supplied to the domestic electric power load (hereinafter referred merely to as load). Then, when the power generation exceeds the power consumption by the load, the excess power generation is fed back and sold to the commercial power grid (hereinafter referred merely to as grid). Then, when the power consumption by the load increases and exceeds the power generation, the shortfall is compensated by the power supplied from the grid.
Furthermore, recently, in order to secure power supply to loads when unforeseen blackout or operation stop occurs on the grid side due to disasters and the like, or to utilize the night power effectively, a distributed power generation system in which excessively generated power is previously stored in a storage battery has attracted attention. Patent Literature 1 discloses a distributed power generation system configured by adding a storage battery to an existing power generation system.